Process for the Production of Naphthenic Process Oils by Hydrogenation

ABSTRACT

The object of the invention is a method for producing naphthenic process oils that have a high content of naphthenic carbon atoms of 20-60 wt % and a low content of polycyclic aromatics of less than 3 wt %, determined in accordance with IP 346, by the hydrogenation of a process oil educt that has a high content of polycyclic aromatics. The method in accordance with the invention enables secondary extracts, such as are formed in the production of label-free process oils, even in a mixture with primary extracts, to be utilized in an economically meaningful way. The resulting process oils are likewise label-free, so that the use of PCA-containing process oils can be reduced and less of these substances will get into the environment. Through this the environment and in particular health are less stressed. In addition, the starting substances in this way can lead to a different use and no longer have to be added to heating oil. By avoiding heating oil, CO 2  emissions are also reduced. Also, through the direct hydrogenation of DAE, high value naphthenic process oils are obtained by the method in accordance with the invention. The process oils that are obtained contain surprisingly high amounts of naphthenic hydrocarbon compounds. In addition, an object of the invention is the use of the process oils produced in accordance with the invention as a plasticizer or extender oil for natural and synthetic rubber mixtures or thermoplastic elastomers.

The object of the invention is a method for producing naphthenic processoils with a high content of naphthenic hydrocarbons and a content ofpolycyclic aromatics that is less than 3 wt % in accordance with IP 346,as well as the use of these process oils.

Process oils are generally understood to be hydrocarbon mixtures thatboil in the lubricating oil range, but are usually not used as, and alsonot in combination with, lubricating oils. Process oils are obtained inthe refining of petroleum. The crude oil is subjected to an atmosphericdistillation, separating all products that boil up to about 350° C. atnormal pressure. A mixture of bitumens, asphaltenes, waxes, and heavyoils is obtained as residue after the distillation. The heavy oils areprocessed further to various products, which in addition to lubricatingoils also include the process oils, which are chiefly used asplasticizers.

The process oils differ in each case according to their content ofaromatic carbon atoms (C_(A)), naphthenic carbon atoms (C_(N)), andparaffinic carbon atoms (C_(P)), measured in accordance with ASTM D2140. Aromatic process oils in some case have undesirably high amountsof polycyclic aromatics (PCAs). Polycyclic aromatics are understood tobe compounds with more than two condensed aromatic nuclei. Since thepolycyclic aromatics, such as benzo[a]pyrene, are suspected of beingcarcinogenic, even in the past process oils with a high PCA content havebeen used only to a limited extent.

According to European Guideline 769/76, augmented by Guideline 69/2005of Nov. 16, 2005, the use of process oils is now only allowed if theseprocess oils have a content of polycyclic aromatics that is less than 3wt %, measured by the method of IP 346.

Besides the process oils that have a high aromatic content, there isanother group of frequently used process oils, the naphthenic oils.Naphthenic oils are characterized by a high content of cycloalkanes, butcan also have a higher content of aromatic hydrocarbon compounds thanparaffinic oils. Correspondingly, naphthenic oils exhibit better solventproperties with respect to rubber than paraffinic oils and can beprocessed better. Naphthenic process oils for medicinal use usuallycontain no or only a small content of aromatics.

The corresponding process oils that still contain more than 3 wt %polycyclic aromatics in accordance with IP 346 must in the future eitherbe disposed of as hazardous waste or, if need be, added to heating oil,where this has the disadvantage that higher sulfur emissions arise whenthe heating oil is burned. Because of the changed legislation suchproducts in the future therefore may no longer be added to heating oil,in order to reduce sulfur emissions. If need be, combustion in plantswith special filters will still be permitted. Moreover, extractionresidues with a high content of polycyclic aromatics are formed in theproduction of process oils with a low content of PCAs, for example theprocess oils TDAE and MES. These extraction residues in the future alsomust be disposed of or added to heating oil.

One possibility for obtaining process oils with a low content ofpolycyclic aromatics is to reextract a primary extract that is obtainedby extraction of a lubricating oil distillate that derives from mineraloil. One such process is described in EP 0 417 980 B1. The process oilthat is obtained in this case, for example TDAE, has a polycyclicaromatic content that is less than 3 wt % in accordance with IP 346.However, a disadvantage of this process is that a product with a highconcentration of polycyclic aromatics, from up to 15 and even over 20 wt%, is obtained as secondary extract, i.e., as the “bottom phase,” whichis taken from the second extraction column.

The task of this invention therefore is to make available a method thatallows the processing of process residues that have a high PCA content,where the resulting process oils should be label-free [nonhazardous],i.e., have a PCA content of less than 3 wt %, determined in accordancewith IP 346. The method should allow an environmentally friendly use ofDAE, which is subject to mandatory labeling, the secondary extracts, andthe extraction residues from the production of other process oils.Moreover, the resulting process oils should be of such a qualitativelyhigh grade that they satisfy the standard requirements for the currentprocess oils, for example as plasticizers or extender oils in rubbers orrubber mixtures, as oils in printing inks, as transformer oils, or asfeedstock for the production of high grade oils, for example TDAE,and/or as metalworking oils.

The task is solved in accordance with the invention by a method forproducing naphthenic process oils that have a carbon distribution C_(A)to C_(N) to C_(P) of 0-30 wt % to 20-65 wt % to 20-55 wt %, determinedin accordance with ASTM D 2140, and a content of polycyclic aromatics(PCAs) of less than 3 wt % in accordance with IP 346,

characterized in that

a process oil educt that has a content of polycyclic aromatics of atleast 3 wt %, determined in accordance with IP 346, and a content ofnaphthenic hydrocarbon atoms C_(N)≦25 wt %,

is hydrogenated with hydrogen using a metal catalyst at temperaturesfrom 200-400° C. and pressures from 80-250 bar.

In addition, an object of the invention is the use of a process oil thatis produced in accordance with the invention as a plasticizer orextender oil for rubbers or rubber mixtures that are based on naturaland synthetic rubbers, or for thermoplastic elastomers, as a rawmaterial for technical or medicinal white oils, as printing ink oils, asa release agent for architectural coatings, or industrial fatproduction, transformer oils, or special metalworking oils.

Further embodiments are the object of the dependent claims or aredescribed below.

To conduct the method in accordance with the invention, a process oileduct is passed with hydrogen over a metal catalyst under the indicatedconditions. Preferably, transition metal catalysts on a support are usedas the catalyst. Preferred metal catalysts are cobalt, nickel,molybdenum, chromium, vanadium, nickel-molybdenum catalysts,chromium-vanadium catalysts, metal oxides, metal sulfides, orcombinations thereof. The substances that are conventional in industrysuch as aluminum oxide or zeolites are tried-and-true materials assupport substances. Basically, conventional hydrogenation catalysts canbe used for the hydrogenation.

The hydrogenation is preferably carried out at temperatures of 250-400°C., especially preferably 300-375° C. The reactor is preferably operatedat a pressure of 80-200 bar. The hydrogenation is preferably carried outwith an average residence time of 6-60 min.

When the method in accordance with the invention is carried out, processoils that have a content of naphthenic hydrocarbon atoms C_(N) of 30-65wt %, determined in accordance with ASTM D 2140, are obtained.Surprisingly, process oils whose C_(N) content is >40 or 45 wt %, seeASTM D 2140, can be obtained with the method in accordance with theinvention. According to the current prevailing opinion and incorrespondence with ASTM D 2140, a maximum content of 45 wt % naphthenichydrocarbon atoms is possible in process oils. The resulting processoils in addition have a content of less than 3 wt % polycyclicaromatics, determined in accordance with IP 346.

Process oil educts that have a polycyclic aromatic content >3 wt %,determined in accordance with IP 346, preferably a polycyclic aromaticcontent of 10-30 wt %, are used as the educt for the hydrogenation. Suchsuitable process oil educts are, for example, the secondary extractsthat are obtained in the production of TDAE or MES. One such process isknown from EP 0 417 980 B1. The secondary extract obtained there can beused as starting material for the method in accordance with theinvention. Specific hydrocarbon distributions in the products can betailored through the choice of the educt and possibly by mixingdifferent starting extracts. DAE (distillate aromatic extract) is also asuitable educt for the method in accordance with the invention.

To obtain a traditional TDAE, usually crude oil is subjected toatmospheric distillation to separate gas, naphtha, and kerosenefractions. The atmospheric residue is separated into a vacuum residueand one or more distillates in a vacuum distillation. The distillate isthen, in an extraction with a suitable solvent, separated into araffinate and an extract (primary extract), the DAE. Base oil and waxesare obtained from the raffinate. A second extraction of the primaryextract affords the TDAE, and with an appropriate choice of reactionconditions, one can obtain a process oil that has a polycyclic aromaticcontent ≦3 wt %. In addition, another extract, the secondary extract, isformed in the second extraction. This secondary extract can be used byitself or in a mixture, for example with other extracts or process oils,as the educt for the method in accordance with the invention and iscorrespondingly hydrogenated in an additional process step.

DAE (distillate aromatic extract) is also suitable as the educt for theproduction method in accordance with the invention [for] production ofprocess oils. DAEs are highly aromatic process oils. Examples of DAEsare the products that can be obtained from Klaus Dahleke KG:

Tudalen®65 (C_(A)=40 wt %, C_(N)=25 wt %, C_(P)=35 wt %; PCA inaccordance with IP346>15 wt %)

Tudalen®81 (C_(A)=43 wt %, C_(N)=24 wt %, C_(P)=33 wt %; PCA inaccordance with IP346 >15 wt %).

The naphthenic process oils can be obtained in high yields by the methodin accordance with the invention. For example, high yields up to 100%were obtained in the hydrogenation of DAE. With appropriate conduct ofthe process, environmentally hazardous process oils that are subject tomandatory labeling are no longer produced. Rather, naphthenic label-freeprocess oils can be obtained from the labeling-mandatory andenvironmentally questionable DAE via the method in accordance with theinvention.

In accordance with the invention it is also possible to use othersubstances as process oil educts, provided the sum of C_(A) and C_(N) inthe process oil educt is higher than the sum of the desired C_(N)content plus the residual content of aromatics and/or they have acontent of polycyclic aromatics >3 wt %, measured in accordance with IP346. For example, extracts, mineral oil fractions or process oils, forwhich the sum of C_(A) plus C_(N) is 55, can be used as process oileducts.

In one embodiment of the method, an educt mixture of DAE and secondaryextract is used. It turned out that the glass transition point T_(g) ofthe process oils can be set through the choice of educt mixture.Surprisingly, a process oil produced in accordance with the inventionfrom a DAE/secondary extract mixture, in spite of having the same C_(A)content, has different T_(g) values, depending on the starting mixture.The T_(g) can vary in this case, for example, between −52° C. and +45°C. Mixtures of 75%:25% to 25%:75% secondary extract to DAE arepreferably used. Control of the dynamic properties of the subsequentrubber product is possible through the choice of a process oil with aspecific glass transition temperature.

The method in accordance with the invention thus allows a process oileduct that has a high content of polycyclic aromatics and thus may nolonger be sold in accordance with the new EU Guideline and anyway isquestionable from the standpoint of health and environmental policy, fora high grade product. Moreover, the starting materials can in this waybe sent to a different use and no longer have to be added to heatingoil. By avoiding heating oil, the CO₂ emissions are also reduced.Surprisingly, the resulting naphthenic process oil, in spite of the lowcontent of PCA, still has a high content of aromatic hydrocarbon atomsC_(A), which preferably is between 0 and 30 wt %, determined inaccordance with ASTM D 2140, in each case according to the reactionconditions. Preferably the sum of C_(A) and C_(N) is between 50 and 70.A high content of aromatic hydrocarbon compounds in process oil improvesthe wet skid resistance of an automobile tire and the cornering abilityon dry roads, while a high C_(N) content in the process oil improves therolling resistance of an automobile tire.

The process oil produced in accordance with the invention is used as aplasticizer or extender oil for rubbers and rubber mixtures that arebased on natural and synthetic rubbers, or thermoplastic elastomers. Itlikewise can also be used as raw material for medicinal or industrialwhite oils, as printing ink oil, for example for colored and black inksin newsprint, transformer oil, as release agent in architecturalcoatings, or as special metalworking oils, and it also finds use inindustrial fat production. The process oil produced in accordance withthe invention is especially preferably used as a plasticizer in tires orindustrial rubber goods, as white oil or as metalworking oil, forexample in the drawing of copper wire.

If a DAE is used as the educt for the method in accordance with theinvention, the process oils produced in accordance with the inventionare preferably used as a plasticizer or extender oil for rubbers orrubber mixtures that are based on natural and synthetic rubbers,especially preferably tires.

The method in accordance with the invention is illustrated by means ofthe figures by way of example. Here:

FIG. 1 shows a flowchart of the extraction process known from the priorart for production of TDAE and MES.

FIG. 2 shows a flowchart of one embodiment of the method in accordancewith the invention.

FIG. 3 shows a flowchart of another embodiment of the method inaccordance with the invention.

FIG. 1 shows the second extraction step of the conventional extractionfor production of TDAE or MES. The primary extract 2 is sent to anextraction column 1. The primary extract is a mixture of differenthydrocarbon compounds, including aromatic hydrocarbon compounds andpolycyclic aromatics. At the same time solvent is supplied to theextraction column via line 3. The raffinate 4, for example a TDAE orMES, is taken from the top of the column. At the same time a secondaryextract 5, which has a high content of polycyclic aromatics, is takenfrom the bottom of the column.

FIG. 2 shows the course of the method in accordance with the invention.A process oil 5 with a high polycyclic aromatic content, as obtained,for example from the method shown in FIG. 1, is sent to a hydrogenationreactor 6 and hydrogenated there with hydrogen. A naphthenic process oil7 and stripping oil 8 are taken from the hydrogenation reactor 6. Thenaphthenic process oil 7 has a PCA content below 3 wt %. In a lesspreferred embodiment, the method can also be conducted so that endproducts with a relatively high residual content of aromatics, the PCAcontent of which can be >3 wt % in accordance with IP 346, are obtained.These relatively high-aromatic fractions can be added via line 9 to theprimary extract 2 or, alternatively, can be sent to the extractioncolumn 1 and are suitable as feedstock for the production of label-freeprocess oils either by itself or in a mixture with primary extract.

FIG. 3 shows the production of a naphthenic process oil 7 by directhydrogenation of a primary extract 2 in a hydrogenation reactor 6. Inaddition to the naphthenic process oil 7, a stripping oil 8 is obtained.A crude oil 10 is subjected to atmospheric distillation 11. Theresulting atmospheric residue 12 is solely processed further in a vacuumdistillation 13. A distillate 14 and a vacuum residue 15 are obtained.The distillate 14 is separated into the primary extract 2 and araffinate 17 in an extraction column 16.

EXAMPLES Example 1

A secondary extract with a polycyclic aromatic content of 45 wt %according to IP 346 and C_(N) content of 22 wt % and C_(P) content of 23wt % was input with hydrogen to a hydrogenation reactor at a temperatureof 340° C. and pressure of 200 bar. The reactor contained anickel-molybdenum catalyst (Axens HR548, Evonik). Hydrogenation wascarried out at an average residence time of 25 min. 94% naphthenicprocess oil and 6% stripping oil were obtained.

The resulting naphthenic process oil has the properties given in Table1.

TABLE 1 Properties of resulting naphthenic process oil from Example 1Properties of process oil in accordance with Example Benz[a]pyrene [ppm]<1 Sum PAH [ppm] measured by RL 2005/69 <10 EC Viscosity at 40° C.[mm²/s] 612 Viscosity at 100° C. [mm²/s] 39 C_(A) according to ASTM D2140 [wt %] 3 C_(N) according to ASTM D 2140 [wt %] 57 C_(P) accordingto ASTM D 2140 [wt %] 40 Aniline point [° C.] 93

Example 2

In addition, the properties of different products that [were] obtainedby the method in accordance with the invention were compared with thoseof a traditional process oil TDAE. Table 2 shows a comparison of thedifferent production conditions and data for three products produced inaccordance with the invention (hydrogenation products) in a comparisonwith a TDAE. The hydrogenation products were prepared analogously to theexample described above. The mixture of primary extract to secondaryextract was 50:50.

TABLE 2 Production conditions and properties of process oils produced inaccordance with the invention and a comparison process oil HydrogenationHydrogenation Hydrogenation products from products from products fromVivatec ® 500 primary extract primary/secondary secondary Method ofdetermination (TDAE) (DAE) extract mixture extract Catalyst Axens HR 548Axens HR 548 Axens HR 548 A1024 A1024 A1024 Reaction 310 330 350temperature [° C.] Pressure 200 200 200 [bar] Residence time 18 18 16[min] DMSO extract IP 346 2.6 2.8 2.9 2.8 [%] Benzo-(a)pyrene GC-MS 0.40.3 0.1 0.5 [ppm] Total PAH GC-MS 5.7 2.5 3.1 4.2 [ppm] Viscosity at DIN51562 21.1 19.1 12.6 20.8 100° C. T. 1 [mm²/s] Sulfur DIN EN ISO 1.030.15 0.12 0.10 [%] 14596 CA DIN 51378 25 24 25 24 [%] CN DIN 51378 30 3342 48 [%] CP DIN 51378 45 44 33 28 [%] AP DIN ISO 2977 70 70 64 61 [°C.]

The process oils that were obtained were worked into compounds (rubbermixtures). The composition of the compounds can be seen from Table 3.

TABLE 3 Composition of compounds Raw material Product, manufacturerComparison Example 2a Example 2b Example 2c Buna VSL 5025-0 HM SSBR,Lanxess 70 70 70 70 Buna CB 24 NdBR, Lanxess 30 30 30 30 Ultrasil 7000GR Silica, Evonik 80 80 80 80 SI 75 Silane, Evonik 5.8 5.8 5.8 5.8 CoraxN 223 Soot, Evonik 10 10 10 10 Vulkanox 4020/LG 6PPD, Lanxess 1 1 1 1Vulkanox HS/LG TMQ, Lanxess 1 1 1 1 Rotsiegel zinc white ZnO, Grillo 3 33 3 Stearic acid 1 1 1 1 Vulkacit D/C Sulfenamide, Lanxess 2 2 2 2Vulkacit CZ/C Sulfenamide, Lanxess 1.5 1.5 1.5 1.5 Sulfur 1.8 1.8 1.81.8 Vivatec 500 TDAE oil, H&R 37.5 Hydrogenation 37.5 products fromprimary extract Hydrogenation 37.5 products from primary/secondaryextract mixture Hydrogenation 37.5 products from secondary extract

The compounds were vulcanized and the properties of the resultingvulcanizates were measured. These are given in Table 4.

TABLE 4 Hardness, rebound elasticity, delta tangent and wear ofresulting vulcanizates Exam- Exam- Exam- Comparison ple 2a ple 2b ple 2cHardness Shore A hardness 60 62 61 61 A/D at 23° C. Standard Shore Ahardness 59 59 60 54 at 70° C. Rebound R (23° C.) 33.5 32.2 31.5 30.8elasticity R (70° C.) 55 54 55 57 Tensile Breaking 440 425 405 385 testelongation: Bar S2 Breaking stress: 18.5 18.1 17.9 17.6 Tangent  0° C.0.52 0.50 0.47 0.48 delta 60° C. 0.13 0.13 0.12 0.11 Wear DIN 53516 wear102 105 108 109

It turns out that through the hydrogenation of the said raw materialsprocess oils are obtained that have values that are absolutelycomparable to a TDAE. One can see that with an increase of the NAPcontent the rolling resistance (tangent delta @ 60° C.) becomes betterwith an increase of the NAP content, while wear and wet slip resistance(tangent delta @ 0° C.) become better with a decrease of the NAPcontent. This puts the user in a position to be able to adjust the saidkey properties selectively and not just in the case of tires. Suchadjustment up to now was not possible with the traditional process oils.

1. A method for producing naphthenic process oils that have a carbondistribution CA to CN to CP of 0-30 wt % to 20-65 wt % to 20-55 wt %,determined in accordance with ASTM D 2140, and a content of polycyclicaromatics (PCAs) of less than 3 wt %, in accordance with IP 346, whereina process oil educt that has a content of polycyclic aromatics of atleast 3 wt %, determined in accordance with IP 346, and a content ofnaphthenic carbon atoms CN≦25 wt %, is hydrogenated with hydrogen usinga metal catalyst at temperatures of 200-400° C. and pressures of 80-250bar.
 2. The method as in claim 1, wherein the hydrogenation is carriedout at temperatures of 250-400° C.
 3. The method as in claim 1, whereinthe metal catalyst [is] based on a nickel, cobalt, molybdenum, chromium,vanadium, nickel-molybdenum, chromium-vanadium catalyst, a metal oxide,a metal sulfide, or a mixture thereof.
 4. The method as in claim 1,wherein the naphthenic process oil that is produced has a content ofnaphthenic carbon atoms CN of 30-65 wt %.
 5. The method as in claim 1,wherein the average residence time is 6-60 min.
 6. The method as inclaim 1, wherein the process oil educt that is used is a secondaryextract from the production of TDAE or MES.
 7. The method as in claim 1,wherein the process oil product that is used is a DAE.
 8. The method asin claim 1, wherein the process oil educt that is used is a mixture ofsecondary extract and DAE, preferably a mixture of 75 wt % to 25 wt % upto 25 wt % to 75 wt % secondary extract to DAE.
 9. The method as inclaim 1, wherein the aniline point of the naphthenic process oil isbetween 30 and 115° C., determined in accordance with DIN ISO
 2977. 10.The use of a process oil produced as in claim 1 as a plasticizer orextender oil for rubbers or rubber mixtures that are based on natural orsynthetic rubbers, or for thermoplastic elastomers, for industrial fatproduction, as a raw material for industrial or medicinal white oils,printing ink oils, release agents in building protection, transformeroils, or special metalworking oils.
 11. The method as in claim 2,wherein the hydrogenation is carried out at temperatures of 300-375° C.